Stock Plan and Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Option Activity Includes Options Granted

The following table, which includes options granted under the 2015 Plan, 2018 Plan and the Non-Plan Option, summarizes option activity:

	Shares Subject to Outstanding Options			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2018		1,458,080		$	7.55
Options granted		3,967,746		$	9.66
Options exercised		(41,762	)	$	4.85
Options forfeited or canceled		(646,060	)	$	10.01
Outstanding at December 31, 2019		4,738,004		$	9.00		8.83	$	8,174
Options vested and expected to vest as of December 31, 2019		4,738,004		$	9.00		8.83	$	8,174
Options exercisable as of December 31, 2019		1,145,303		$	8.52		7.97	$	2,851

Summary of Non-Vested Restricted Stock

A summary of the Company’s non-vested restricted stock for the periods presented is as follows:

	Number of Shares		Weighted Average Grant Date Fair Value		Remaining Contractual Term (Years)
Balance, December 31, 2018		289,352	$	0.000396		0.4
Vested during the year		289,352	$	0.000396
Balance, December 31, 2019		-	$	-		-

Summary of Employee and Non-Employee Stock-based Compensation Expense

The following table summarizes employee and non-employee stock-based compensation expense for the years ended December 31, 2019 and 2018, and also the allocation within the consolidated statements of operations and comprehensive loss (in thousands):

	Year Ended December 31,
	2019		2018
Research and development	$	4,152	$	2,255
General and administrative		4,829		1,619
Total stock-based compensation	$	8,981	$	3,874

Schedule of Assumptions Used to Calculate Fair Value of Stock-Based Compensation

The following assumptions were used to calculate the fair value of stock-based compensation for the years ended December 31, 2019, and 2018:

	Stock Options		ESPP
	Year Ended December 31,		Year Ended December 31,
	2019	2018	2019	2018
Risk-free interest rate	1.6% - 2.3%	1.2% - 3.1%	1.6% - 2.3%	2.1% - 2.6%
Expected term (in years)	6.02	5.16-9.95	0.5-2.0	0.5-2.0
Volatility	71.8% - 74.6%	58.7%-75.5%	64.8% - 77.1%	54.3% - 65.5%
Dividend yield	0%	0%	0%	0%